How to set SPX variable output value?

SPX17, SPX78 and SPX79 are available with variable output by adding a resistor here:

When shipped, variable SPX has Vout=30V, so add a resistor to set the correct voltage before you
connect it and power it on!

Fixed and variable output SPX, the only
difference is if we add the extra resistor or if you add it. We add a thin film 0603 SMD, you can use
a ¼W resistor of your technology choice. The additional resistor is in parallel with a 10k
resistor so Vout change is not linear with resistance change.

Calculate Rset in kΩ as

Typical values are

Vout

Rset

Nearest1% value (Ohms)

Nominal Vout

5

0

0

5

6.3

548.52

549

6.3

7

869.57

866

6.99

8

1363.64

1370

8.01

9

1904.76

1910

9.01

10

2500

2490

9.98

12

3888.89

3900

12.01

12.6

4367.82

4320

12.54

15

6666.67

6650

14.98

16

7857.14

7870

16.01

18

10833.33

10700

17.92

20

15000

15000

20

24

31666.67

31600

23.99

30

none

none

30

You can use a potentiometer to set Vout. A 50k trimmer will adjust from
25.8V to 5V, a 100k trimmer will adjust from 27.7V to 5V. The
trimmer is in parallel with a 10k resistor so Vout change is not
linear with resistance change.